(1) In addition to the modes of procedure hereinafter prescribed in particular cases and classes of cases, said commission shall have power to prescribe rules of procedure and to do all things necessary and convenient in the exercise of the powers conferred by this chapter upon the commission; provided that nothing in this chapter shall be construed as vesting judicial powers on said commission or as denying to any person, firm, association, corporation, municipality, county, town, or village the right to test in a court of competent jurisdiction the legality or reasonableness of any fixed order made by the commission in the exercise of its duties or powers.
(2) The commission shall have the power to:
(a) adopt reasonable and proper rules relative to all inspections, tests, audits, and investigations;
(b) adopt and publish reasonable and proper rules to govern its proceedings; and
(c) regulate the mode and manner of all investigations and hearings of public utilities and other parties before it.